Method for producing a part using a deposition technique

ABSTRACT

The invention relates to a method for producing a part using a deposition technique. A layered composite is built up in layers, the individual layers each containing particulate material and binding material as well as optionally, a treatment agent. The layers maintain a predetermined porosity. The layer composite is built up in the absence of hardening agent. Once construction is complete, the layer composite is hardened.

This invention relates to a method for producing a part in layers usinga deposition technique to build a layered composite containing the partmade of a particulate matter. The part produced is either a castingmould or core. The method is also suitable for manufacturing a metalpart from a particulate metallic material, such as a metal powder or agranular synthetic material.

A conventional method for producing patterns and/or cores for metalcasting utilizes a mixture of sand with a hardening binder filled in abox. A positive pattern for making the metal casting is embedded in thesand-binder mixture prior to its curing and is then removed again. Thisleaves an impression in the sand-binder mixture, which represents anegative pattern of the casting. The pattern of the sand-binder mixtureis cured such that an adequately resistant mould of the negative patternis produced.

Another alternative approach for manufacturing castings utilizes eithera mixture of sand and binder also called Croning sand, which is aparticulate matter made of moulding sand, such as quarts or zircon sand,pre-coated with a synthetic resin.

The bonding of the particulate matter is achieved by smelting the drybinder with applied heat. The attendant energy required for making thecasting cores or moulds is thus not insignificant. Besides, the methodrequires use of relatively complex machines.

Cold curing techniques, such as the Cold Box method, are advantageous,in terms of energy savings for pattern fabrication. Here, the binder iscored chemically. This is done either with the addition of a cold-curingdual-component binder into the moulding sand, which remains workable fora limited time period before it hardens, or the pattern from thesand-binder mixture is alternatively flooded with a curing gas thatcures the binder. The latter is referred to as a gas curing technique.

Conventional pattern making methods as described above then finish thepositive pattern in an NC milling machine or NC lathe, which isespecially time-consuming and expensive with increasing complexity ofthe desired metal part.

With a layered deposition technique, also called rapid prototyping inwhich the pattern making material is deposited in layers, it is possibleto produce the castings, moulds, or other parts faster and morecost-effectively.

A known method for building a part in layers is described in U.S. Pat.No. 5,182,170 (Marcus et al). In this method, a layer of abinder-containing powder is deposited on a base. This layer is thensubjected to a reactive gas atmosphere, which activates the binder. Inthis activating atmosphere, a predefined subarea of the layer is heatedlocally. The reactive gas and the added heat interact with the binder,initiating a localized chemical reaction of the binder leading toconsolidation of the layer in the particular location. A laser, forexample, could be the heat source. The powder deposition and subsequentactivation and consolidation are carried out layer-by-layer until thepart is finished.

Another layer deposition technique is known from the patents U.S. Pat.No. 5,204,055 and EP-0 431 924 B1 (Sachs et al). In this method, a layerof a particulate building material (e.g. ceramic or metal) is deposited.Through selective application of a self-curing binder in a predefinedsubarea of each layer, the building layer is bonded in the selected areaand also bonded to the previously formed layer, before the next layer isdeposited. This process is repeated in layers to produce a layeredcomposite, in which the part to be made is contained within particulatematter is loose, since it has not been wetted with a binder. The bindercan be applied as droplets through a printing technology device known asa Drop-On-Demand dispensing head, such as an inkjet print head, which isguided in a controlled manner by a predetermined program. The predefinedsubarea of each layer is consolidated at least partially, throughapplication of heat radiation or by a chemical reaction of the binder,prior to deposition of the subsequent layer. Following building of thelayered composite, post-treatment with applied heat can be conducted tofully consolidate all subareas forming the part.

A problem with the EP-0 431 92 4 B1 (Sachs) method relates to thebinder's self-curing property, which can affect the cohesion betweensuccessive layers. Additionally, the binder in the Drop-On-Demand printhead tends to cure and block the print head, making frequent cleaning ofthe print head necessary.

A rapid prototyping method described in DE 198 53 834.0 (Höchsmann etal.) involves depositing a layer of a particulate matter, the entiresurface of which is then covered with a binder. Prior to depositing thenext layer, a curing agent is applied to selected subareas of the layertreated with a binder, whereby the binder hardens in those selectedsubareas. The curing agent is, for instance, applied with aDrop-On-Demand print head. The curing agent does not harden without thebinder, and thereby the print head nozzles do not get blocked with ahardening material. A layered composite comprised of many layers isaccordingly built layer-by-layer.

Another rapid prototyping method is described in DE 197 23 892.0(Höchsmann et al.), in which a layer of a packable particulate buildingmaterial is first deposited on particles pre-coated with a curablebinder. The building material could, for example, be Croning sand. Atreatment agent is applied to selected subareas of each layer, whichmodifies the curing reactivity of the binder within the binder coating.Before deposition of the subsequent layer, energy with a given level ofspecific energy is then applied to this layer. This energy level isselected to match the modified curing reactivity of the binder achievedwith the treatment agent, such that the binder cures in only thelocations treated with the treatment agent. Each layer is accordinglycured before the next layer is added.

This invention fulfils the requirement to provide a rapid prototypingmethod for manufacturing parts, in particular casting moulds and cores,which is cost-effective and combines high manufacturing speed withfabrication precision.

According to the invention, in the method for producing a part in layersusing a deposition technique by building a layered composite containingthe part made of particulate matter comprised of particles of aprescribed particle size, the particulate matter is depositedlayer-by-layer to form, successive layers of a porous bulk, and in atleast one predefined subarea of each layer, which subarea could varyfrom layer to layer, and prior to deposition of the subsequent layer atreatment agent in a free-flowing state is apportioned on each layer.The treatment fluid sets up a bonding process, in which the particles inthe predefined subareas bond firmly to one another, through the bindercontained either in the particulate matter or deposited thereon, in thepresence of an initiator.

According to the invention, however, the layered composite is built inthe absence of an initiator. This initiator is added only after thelayered composite has been completed, such that the bonding process isexecuted only after completion of the layered composite.

For the known methods described above, appropriate actions are necessaryto always ensure that each predefined subarea of each layer isconsolidated at least partially through bonding of the binderimmediately following deposition of a layer and prior to deposition ofthe next layer. During the course of the invention, however, it wassurprisingly discovered that even partial consolidation of thepredefined subarea may not be required, if an effort is made to preventthe free-flowing treatment agent from flowing and spreading out beyondor at least not far beyond the boundaries of the predefined subarea intothe surrounding untreated particulate matter. This can be achievedespecially through appropriate limitation of the treatment agent dosageby matching it to the volume of the predefined subarea as determinedfrom its surface area, layer thickness, and particle size, and therewiththe porosity of the particulate matter and its wettability depending onthe flow characteristics of the treatment agent.

According to the invention, bonding of the particulate matter particlesin the predefined subareas is also achieved with a binder. In theprimary embodiment of the method, it could be the binder itself thatfunctions as the treatment agent, in the form of a free-flowing powderor a liquid, apportioned over the predefined subareas.

In another embodiment of the method, the binder can be applied on thedeposited layer before or after application of the treatment agent overthe full surface, or the binder can be mixed with the particulate matterprior to its deposition, or at least the majority of the particulatematter particles are pre-coated with the binder. In this embodiment ofthe method, the treatment agent is selected such that it modifies thekey binding property of the binder from a specific initial value orinitial range of values, as determined prior to application of thetreatment agent, to a markedly different value or range of values.Hereafter, this key specific property of the binder will be designatedin terms of its reactivity. In this second embodiment of the method, thereaction effectiveness of the initiator is adjusted and set according tothe modified reactivity of the binder, such that the unmodified binderreacts selectively and bonds either to the areas outside of thepredefined subareas treated with the treatment agent, or to thepredefined subareas in which the binder is modified through its contactwith the treatment agent. The treatment agent could thus be a liquidlike hydrochloric acid or such that soaks into the dry binder or altersits composition and thereby makes it more amenable for bonding throughapplication of energy or a chemical reaction, compared with theuntreated binder. For example, the smelting point or range could belowered by a given amount with an appropriately selected treatmentagent, such that when the temperature of the subsequently appliedinitiator lies between the smelting points of an unmodified and amodified binder, selective smelting of the modified binder can beinduced. Another possibility is that the treatment agent is a chemicalcatalyst or an inhibitor, with which the modified binder's chemicalreactivity for chemical bonding or a curing reaction with a chemical gasor fluid, depending on its concentration and temperature, is increasedor reduced by the given amount.

In this second embodiment of the method, it is preferred to use aparticulate matter pre-coated with the binder, such as Croning sand.This sand contains a minimal quantity of a binder enveloping eachparticle, making it essentially necessary to apply the treatment agentonly in a quantity adequate to attain appropriate wetting of thesheathing at the reciprocal contact points of the particles.

The initiator could be an immaterial medium like energy in the form ofheat or radiation. The initiator could also be a material medium like aliquid or gaseous heat transfer agent or chemical reaction agent. Thebinder is preferably cured chemically calling for the use of a heatingor a chemical curing agent that leads to linkage of the binder. Theinitiator could also be an energy medium and a material liquid at thesame time.

It is preferred to apply the treatment agent on to the particulatematter, deposited as a porous bulk with a particle size dependentporosity, such that the predetermined minimum porosity is maintained inthe predefined subareas, which can then be exploited to finally floodthe layered composite with a liquid or gaseous initiator. Such floodingof the layered composite could possibly be promoted and aided byevacuating the layered composite in an enclosed container prior to theflooding.

The method according to the invention has several advantages:

A bonding process and especially hardening of the binder can lead toshrinkage. If thermal bonding or hardening is implemented separately foreach layer, stresses will be generated in the layered composite, whichcould lead to distortion or damage of the part. Since according to theinvention, the bonding takes place at the end and not separately foreach layer, if volumetric shrinkage occurs, the entire composite willshrink and become smaller overall, without generating any stresses. Anyshrinkage can be compensated for through inclusion of an appropriateshrinkage mass when specifying the size of the relevant subarea forapportioned application of the treatment agent.

Since the bonding or curing is done after producing the whole layeredcomposite and not after depositing each layer, no bonding step isrequired per layer and the fabrication time for each layer isaccordingly reduced. Bonding of the layered composite requires just onesingle step at the end of the process, which also enhances themanufacturing speed.

Additional time is also saved, since there is no need to wait until eachlayer is bonded or particularly hardened.

Additionally, the final bonding of the layered composite can be executedat a location, other than where the layered composite is built, whichthereby necessitates waiting only for building of the next layeredcomposite rather than waiting for the former one to harden. Accordingly,the layered composite is built preferably in a container to hold thelayered composite together without allowing it to fall apart both duringbuilding and after it is finished, and also for transporting it to thebonding location. During the bonding process, the layered compositecould thus remain in the same container in which it was built.

Another advantage of this method is that the deposition devices forapplying the binder and/or treatment agent cannot become blocked bycuring agents.

Another advantage of the method according to the invention lies thereinthat the building material outside of the predefined subareas can remainuntreated, thereby allowing it to be reused easily after being removedfrom the bonded part. Besides, when the building material is used in anuncoated form, cleaning of the deposition devices utilized for themethod becomes easy. Moreover, the method is more cost-effective, sincethe binder is deposited only on the spots where the part is subsequentlyformed.

The preferred building materials for a method to produce casting mouldsand cores and for a deposition technique are typical sands such asquartz, silicate, chromite, olivine, or zircon sand. Any otherappropriately packable particulate material, or a mixture of differentsands can also be used.

For the above-described second embodiment of the method, it is preferredto use pretreated sand, such as Croning sand precoated with a binder.

Untreated materials have the advantage that they are more cost-effectivethan materials pre-treated with a binder.

The prescribed particle sire, which is the size of the sand grains inthe case of sand, lies preferably in the particle size range from 90 to200 μm, and therein preferably in the range of 110 to 160 μm. It is alsopossible to use smaller or larger particles. Air movements, however,easily affect very small particles, thereby hampering homogeneousdeposition of the particles. Small particles additionally reduce theporosity and impact the gas blast when pouring. On the contrary, extralarge particles result in undesirable surficial graininess of thefinished part. Typically, the median particle diameter or averageparticle size is approximately 140 μm. Normally not all particles are ofthe same size, but instead exhibit a certain sire distribution. Thepreferred quartz sand has an average grain or particle size of 140 μm,with approximately 5% of the grains ranging from 180 to 200 μm in size,59% from 125 to 180 μm, 30% lying between 90 and 125 μm, and 1% of thegrains being smaller than 63 μm. This type of quartz sand, as a buildingmaterial, is typically deposited at a bulk density of 1.32 t/m².

The thickness of each layer of particulate material can vary. Thinnerlayers enable the part to be produced with a higher resolution of itsdesign details. With very thin layers, however, reducing the layerthickness further does not result in any increase in the resolution,since process fluctuations limit the achievable resolution. Conversely,extremely thin layers result in lower fabrication speeds, since manylayering steps become necessary. Thicker layers raise the achievablemanufacturing speed, but all layer thicknesses are also not feasible.Very thick layers make it difficult to apply the treatment agentuniformly on the particulate matter, such that these work steps takelonger and either the fabrication speed does not improve markedly with agreater layer thickness, or it may even drop. Besides, the applicationof thick layers results in poorer resolution of the part's designdetails. The preferred layer thickness is in the range of 0.15 to 0.30mm, making it possible to not only attain a relatively highmanufacturing speed, but also adequate cohesion between the successivelayers and an appropriate resolution of the part's details.

The layer thickness can be varied during manufacturing of the part.Hence, to raise the fabrication speed thicker layers can be selected forareas of the part with fewer design details. In areas of the part withcomplicated and finer design details, the layer thickness can be loweredto enhance both the resolution and manufacturing precision.

The treatment agent is apportioned on to the previously depositedbuilding material layer, such that the building material is just wetted,without any inhomogeneous distribution and local accumulation of thetreatment agent, which would lower the performance of the part builtaccording to this method.

The treatment agent and binder are applied in an amount such that theparticle layer has a residual porosity, whereby the curing agent canpenetrate into the part through these remaining pores during thesubsequent curing stage.

The prescribed binder dosage is preferably selected to maintain a binderto building material weight ratio of less than 6%, and thereinpreferably between 2 and 3%. The amount of binder applied relative tothe building material can vary from layer to layer.

It is preferred to select a similar weight ratio between the treatmentagent and the building material.

If the part is a casting mould or core, the residual porosity of thebonded part that remains after hardening has the added effect that thegases formed under a subsequent casting process can escape. In such asituation, the binder and/or treatment agent are preferably apportionedsuch that, on the one hand, the pattern used to produce a casting out ofa molten mass withstands the pressure of the molten mass, as long as itis not set, and on the other hand, at the point where the molten mass ispartially solidified such that the casting is essentially stable, thebinder and/or treatment agent should have almost vaporized. Once thecasting has solidified, the pattern can be simply destroyed without anysignificant effort to remove it, as in a lost pattern process.

The binder and/or treatment, agent could be applied in a fluid state.

The liquid binder and/or treatment agent can, for example, be applied onthe particle layer as a spray. However, it is preferred to apply thefluid binder and/or treatment agent as liquid binder droplets with aprescribed droplet diameter. The prescribed diameter of the binderand/or treatment agent droplets lies preferably in the size range from50 to 100 μm. For droplets with a diameter of less than about 5 μm,anti-gravitational fractional forces of the air cannot be neglected,thereby making it difficult to dependably deposit the droplets on to thebuilding material. Conversely, large drops result in inhomogeneousdistribution of the liquid in the building material layer.

In such situations, the binder and/or treatment agent should be fluidenough to enable the prescribed dosage to be applied on to the buildingmaterial layer and such that they utilize the capillary action in theparticle interstices for spreading out and wetting the particles.Accordingly, the viscosity of the liquid binder and/or treatment agentis preferably in the range of 1 to 25 mPas, when applied. Additionally,in order that coloured patterns could also be produced, the binder couldcontain a colouring agent, especially a pigment, or alternatively itcould impart a specific colour to the powdered material. Use of severaldifferent coloured binders, each specifically apportioned like thecolour mixing done in an inkjet system, it becomes possible to makefully coloured patterns or ones with colour schemes, for manufacturingapplications calling for interesting display patterns or quite realisticreplicas.

The operating temperature for implementing this method is determined bythe material properties, for instance the viscosity and smelting pointof the building material, binder, or treatment agent used. The method isconducted preferably at temperatures between 10 and 40° C. It isadditionally preferred to use a binder and/or treatment agent that allowthe method to be conducted at room temperature, to minimize unnecessaryequipment complications. Hence, the viscosity of the binder and/ortreatment agent lies preferably in the stated range of 1 to 25 mPas at atemperature of 20° C.

When applied, the binder and/or treatment agent could be at the ambienttemperature or alternatively slightly above that, to reduce theviscosity for eased distribution of the binder and/or treatment agentinto the layer. The ambient temperature refers to the temperature in theimmediate vicinity of the location where the part is produced, forexample, the atmospheric temperature in the close environs thereof.

Alternatively, to promote distribution of the binder and/or treatmentagent in the layer, the layer itself could be heated each time prior toapplying the binder and/or treatment agent.

Instead of as a fluid, the binder and/or treatment agent couldoptionally be applied also as a fine powder with binder and/or treatmentagent particles of a prescribed size. As such, the particle size of thebinder and/or treatment agent should be smaller than that of thebuilding material, in order that the binder and/or treatment agentparticles can wet or envelop the building material particles. Copyingmachines, for example, successfully deposit fine particulate materialswith a toner on to paper, just as sublimation printers apply colouredpowders on paper. In a copying machine, the toner is fixed throughheating, although the toner clings to the paper on being applied evenwithout being fixed.

The liquid or particulate binder and/or treatment agent, for instance,could be applied with the known airless technique, in which a purebinder and/or treatment agent are squeezed under high pressure through anozzle. Alternatively, the binder and/or treatment agent could beapplied with the airbrushing technique, in which the binder and/ortreatment agent are fed to a tip, where a fast moving air stream flowingby or alternatively a rotation technique sweeps it along. Alternatively,the treatment agent could be applied with an ultrasonic sprayer, inwhich a piezo-activated membrane generates droplets of the treatmentagent, which can be targeted precisely with an air stream on to thepredefined subarea of the building zone. With these techniquesmentioned, the binder and/or treatment agent can be apportioned veryprecisely. The binder and/or treatment agent could alternatively beapplied with a silkscreen printing technology or with a technique tospray on the binder and/or treatment agent through a mask. A particulatebinder and/or treatment agent could alternatively be sprinkled on.

A Drop-On-Demand print head, operated for example through a bubble jetor a piezo technique, such as is known for an inkjet print head, ispreferred for applying the fluid or particulate binder and/or treatmentagent.

When applying a liquid binder and/or treatment agent, it is preferred touse a Drop-On-Demand print head for application at a droplet linedensity in the range of 300 to dpi.

The preferred material for the binder and/or treatment agent to beapplied is at least one from the material group that includes sodiumsilicate, phenol resin, polyisocyanate, polyurethane, epoxy resin, furanresin, polyurethane polymer, peroxide, polyphenol resin, or resol ester.

A gas, a liquid, or a liquid vapour could be applied as the curingagent.

Once all the layers of the part to be produced are deposited and thebinder and/or treatment agent have been applied, the liquid curing agentis flooded throughout the part. The curing agent penetrates through theresidual pores of the part that remain after application of the binderand/or treatment agent.

In this way, the binder and the binder treated with the treatment agentare cured.

The curing can be accelerated through heating of the fluid and/or thecomplete part. If a heated vapour is applied when using vapour curing,the heat of the vapour could promote and/or accelerate the curing.

The preferred curing agent for application is at least a gas from thegroup of gases that includes carbon dioxide, dimethylethylamine,triethylamine, sulphur dioxide, methylformiate,formaldehyde-dimethylacetate, or isocyanate.

The appropriate binder and/or treatment agent are accordingly selectedsuch that the resulting material combination is one with which thebinder can be cured.

The following table lists some of the known binder and curing agentcombinations, which can also be applied according to the invention:

TABLE 1 Method Binder Curing Agent CO₂ Sodium silicate Carbon dioxideCold Box Polyure- Phenol resin and Dimethylethylamine thanepolyisocyanate or triethylamine Cold Box Plus PolyurethaneDimethylethylamine SO₂ Furan resin and per- Sulphur dioxide oxide FRCPolyurethane polymer Sulphur dioxide and peroxide Pep Set Polyphenolresin and Methylformiate an acid

The Cold Box Plus technique is normally conducted at a slightly elevatedtemperature of 65 to 70° C.

Nevertheless, other material combinations are feasible. When using anisocyanate as the bindery steam can be applied as the curing agent.

The method according to the invention is suited for producing differenttypes of parts, such as design or construction models. It is preferredto apply the method to produce a casting mould or core, thereinpreferably a mould.

The preferred embodiment of the invention will now be explained in moredetail with reference to the accompanying drawings, in which:

FIG. 1 a is a schematic sectional representation of a part producedaccording to a preferred embodiment of the invention through theapplication of a binder and/or treatment agent;

FIG. 1 b illustrates the fully completed part of FIG. 1 a, and

FIG. 2 shows a device for implementing the method according to theinvention during operation of the dispensing head.

FIG. 1 a depicts a schematic sectional view of a part produced accordingto a preferred embodiment of the invention, such as a casting mould orcore, through deposition of the binder, thereby illustrating theprinciple of the method. According to the method for building the part,a series of n layers are produced sequentially from s1 through sn.Accordingly, the first step involves depositing the first building layers1 over the entire surface. In the next step, the binder and/ortreatment agent are applied on a selected subarea t1 (hatched) of thefirst layer s1. These two steps are then repeated in sequence for theremaining layers s2 through sn. The subareas t1, tj for the differentlayers s1, sj are generally different, but they at least overlap eachother partially such that they are firmly bound to each other.

Once the binder and/or treatment agent have been applied on the lastlayer, the entire part is flooded with the curing agent and therebyhardened. As a helpful measure, the layered composite can be evacuatedprior to application of the curing agent. Finally, the loose buildingmaterial lying outside of the areas t1 to tn is removed, resulting inthe finished part shown in FIG. 1 b.

To produce a pattern with the method according to the invention, thebuilding material is deposited as described above. Conversely, thebinder and/or treatment agent are applied outside of the subareas t1,i=1 . . . n respectively. These areas outside t1 are accordinglyconsolidated through final curing. Once the part has hardened, the looseparticulate matter in the subareas i, i=1 . . . n is re-moved, with theresult that the remaining part reflects a hollow space in the shape ofthe body of FIG. 1 b.

A device for producing parts according to a preferred embodiment of theinvention is shown in FIG. 2. Such a device is comprised of thefollowing components;

-   -   A vertically movable building platform 1,    -   A control mechanism,    -   A horizontally movable deposition device 2 steerable with the        control mechanism, with which a packable building material can        be deposited in layers on building platform 1 or on to a        previous layer up to a prescribed layer thickness, and a        horizontally movable dispensing head 3 arranged on a slide 42,        which is steerable with the control mechanism and with which a        liquid or particulate binder and/or treatment agent can be        applied to a selected area of the layer.

The building material deposition device 2 is arranged with a long box21, open above and below, designed for receiving and depositing thebuilding material on to building platform 1 and on to the last depositedlayer. In the vicinity of the lower open edge of box 21 facing buildingplatform 1 is an outlet device 22 with an opening that can be adjustablyopened or closed and which is arranged with coating blades. Depositiondevice 2 is movable at a settable velocity perpendicularly to the longdirection of box 21, as depicted by axis y in FIG. 2, from one end ofbuilding platform 2 and back.

Slide 42 with dispensing head 3 for applying the binder is movable in amanner similar to the building material deposition device 2, Dispensinghead 3 is movable perpendicularly, as depicted by axis x in FIG. 2, tothe movement direction of slide 42, such that dispensing head 3 can bemoved throughout the entire level above building platform 1.

This method is implemented with the device according to a preferredembodiment of the invention, as follows.

Deposition of building material layers:

On commencement of the procedure, deposition device 2 with box 21 filledwith the building material, as shown in FIG. 2, is positioned at theinitial edge of building platform 1. The outlet device 22 of box 21 isopened to deposit a strip of the building material. At the same timedeposition device 2 is driven to the opposing edge of building platform1 at a constant velocity, such that all of building platform 1 iscovered with a uniform layer of the building material. Box 21 is therebymoved over building platform 1 in such a manner as to use its lower edgeto smooth out the building material layer already deposited. Thevertical position of building platform 1 with respect to box 21 is setsuch that the building material layer attains a predefined desiredthickness, following smoothing out of the layer by the blade located onthe lower edge of box 21. The velocity and/or the degree of opening ofthe deposition device 22 is accordingly preferably selected and set bythe control mechanism such that precisely the amount of buildingmaterial necessary to obtain the predefined layer thickness lands onbuilding platform 1. As soon as deposition device 2 reaches the opposingedge of building platform 1, the material feeding process isinterrupted.

Application of the binder and/or treatment agent:

Dispensing head 3, preferably a Drop-On-Demand dispensing head knownfrom inkjet printers, is moved along a prescribed path over buildingplatform 1, through movement of slide 42 relative to building platform 1and through movement of dispensing head 3 relative to slide 42.Simultaneously, dispensing head 3 ejects the binder and/or treatmentagent. This leads to creation of a pattern with the binder and/ortreatment agent in the building material layer, which reflects thepart's cross-section through the layer level.

The first layer is now complete and a second layer is to be deposited.Accordingly building platform 1 is moved a given distance downwards fromthe deposition device 2. A second layer of building material is thendeposited and imparted a pattern with the binder and/or treatment agent.

Additional layers are made in the same way until a layered composite isfully built.

The layered composite is finally cured, preferably analogous to aconventional gas curing technique.

For example, following deposition of the last layer and application ofthe binder on to this layer, the layered composite is removed from thedeposition device. The building platform can be removed along with thelayered composite to provide support thereto. The layered composite isthen transferred, possibly with the building platform, to a processingchamber. The processing chamber is then flooded with an appropriate gasto cure the layered composite.

Alternatively, the device for producing a part is integrated into aprocessing chamber, such that the layered composite can be cureddirectly therein.

The layers of the layered composite exhibit sufficient reciprocalcohesion, such that the uncured layered composite can be removed fromthe deposition device without problems.

However, the device can also have a building box in which the layers ofthe layered composite are produced such that the building box is filledup with the layers. The building box serves as a support means for thelayered composite and reduces the danger of damage to the uncuredlayered composite, for instance during transport into a processingchamber for curing.

What is claimed is:
 1. A method for producing a part layer-by-layercomprising the steps of: i. depositing a first layer of particulatematter into a building box having a build platform; ii. selectivelyapplying a particulate binder to a predefined subarea the layer so thatthe layer has treated particulate matter in the predefined subarea anduntreated particulate matter outside of the predefined subarea. whereinthe binder is a free-flowing powder; iii. providing support to both thetreated particulate matter and the untreated particulate matter by thebuilding box so that partial consolidation of the treated particulatematter is not required to prevent the treated particulate matter fromflowing beyond the predefined subarea of the layer; iv. repeating stepsi. through iii. until the part is complete, wherein the buildingplatform provides support for the layered composite and reduces thedanger of damage to the uncured layered composite; v. binding theparticulate matter in the predefined subareas only after step iv. iscomplete matter particles in the predefined subareas is achieved withbinder; wherein the steps of depositing the layer of particulatematerial and applying the particulate binder are done in the absence ofan initiator. 2-13. (canceled)
 14. The method of claim 1, wherein theparticulate material includes sand.
 15. The method of claim 1, whereinthe predefined subarea remains untreated and is removed from the bondedpart.
 16. A part prepared according to claim 1, wherein the part is ametal part.
 17. A method for producing a part layer-by-layer, comprisingthe steps of: i. depositing a first layer of particulate matter into abuilding box having building platform; ii. selectively applying a liquidbinder to a predefined subarea of the layer so that the layer hastreated particulate matter in the predefined subarea and untreatedparticulate matter outside of the predefined subarea, wherein the binderis applied in the form of liquid drops according to an inkjet or adrop-on-demand technique; iii. providing support to both the treatedparticulate matter and the untreated particulate matter by the buildingbox so that partial consolidation of the treated particulate matter isnot required to prevent the treated particulate matter from flowingbeyond the predefined subarea of the layer; iv. repeating steps i.through iii, until the part is complete; wherein the building platformprovides support for the layered composite and reduces the danger ofdamage to the uncured layered composite; v. binding the particulatematter in the predefined subareas only after step iv. is complete byheating the part so that the part is bonded, wherein binding of theparticulate matter particles in the predefined subareas is achieved withthe binder; wherein the steps of depositing the layer of particulatematerial and applying the liquid binder are done in the absence of aninitiator.
 18. The method of claim 17, wherein the liquid binder isselectively applied using an inkjet print head.
 19. The method of claim18, wherein the predefined subarea remains untreated and is removed fromthe bonded part.
 20. A method for producing a part layer-by-layer,comprising the steps of: i. depositing a layer of material including adry binder into a building box having a building platform; ii. applyinga treatment agent to a predefined subarea of the layer so that thetreatment agent soaks into the dry binder and makes the treated bindermore amenable for bonding through the application of heat compared withthe untreated dry binder outside of the predefined subarea; iii.repeating steps i. through ii. until the part is complete; wherein thebuilding platform provides support for the layered composite and reducesthe danger of damage to the uncured layered composite; iv. curing thetreated binder in the part after step iii. is complete by heating thepart so that the part is bonded; and wherein the steps of depositing thelayer of particulate material and applying the dry binder are done inthe absence of an initiator; and wherein the binder is applied as afree-flowing powder.
 21. The method method of claim 20, wherein thematerial including the dry binder is a particulate material having acoating of the binder.
 22. The method of claim 20, wherein the materialincluding the dry binder is a Croning sand.
 23. The method of claim 20,wherein the step of depositing a layer of material including a drybinder includes depositing a material including a metal powder.
 24. Themethod of claim 20, wherein the method includes a step of depositing alayer of particulate material prior to the step of depositing a layer ofmaterial including a dry binder.
 25. The method of claim 20, wherein thematerial outside of the predefined subarea remains untreated and isremoved from the bonded part.
 26. The method of claim 20, wherein thetreatment agent is a liquid.
 27. The method of claim 20, wherein thetreatment agent lowers the melting point or range of the binder.
 28. Themethod of claim 20, wherein the step of curing includes heating to atemperature between the melting temperature of the untreated binder andthe melting temperature of the treated binder for selectively meltingthe treated binder.
 29. The method of claim 20, wherein the treatmentagent increases the chemical reactivity of the binding material.
 30. Ametal part produced by the method of claim
 20. 31. A method forproducing a part layer-by-layer, comprising the steps of: i. depositinga first layer of particulate matter into a building box having buildingplatform; ii. applying a resinous binder to a predefined subarea of thelayer so that the layer has treated particulate matter in the predefinedsubarea and untreated particulate matter outside of the predefinedsubarea; iii. providing support to both the treated particulate matterand the untreated particulate matter by the building box so that partialconsolidation of the treated particulate matter is not required toprevent the treated particulate matter from flowing beyond thepredefined subarea of the layer; iv. repeating steps i. through ii. fordepositing additional layers over the previously deposited layer until amulti-layered part is complete; and v. curing the resinous binder in thepart after step iv. is complete by flooding or flowing a gas curingagent through the part; wherein the steps of depositing the layer ofparticulate material and applying the resinous binder are done in theabsence of an initiator.
 32. The method of claim 31, wherein theparticulate matter has a particle size range from 90 μm to 200 μm; andthe gas curing agent is selected from a group that consists of carbondioxide, dimethylethylamine, triethylamine, sulphur dioxide,methylformiate, formaldehyde-dimethylacetate, or isocyanate.